CVE-2018-5179 in Firefox
Summary
by MITRE
A service worker can send the activate event on itself periodically which allows itself to run perpetually in Firefox before version 60. This allows it to background monitor activity by users such as IP addresses visited.
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Analysis
by VulDB Data Team • 09/07/2023
The vulnerability described in CVE-2018-5179 represents a critical flaw in Firefox's service worker implementation that enables persistent background execution of malicious code. Service workers are intended to provide background processing capabilities for web applications, but this vulnerability allows a compromised service worker to continuously activate itself without proper termination mechanisms. The flaw exists specifically in Firefox versions prior to 60, where the service worker activation cycle lacks adequate safeguards to prevent infinite looping or prolonged execution. This design weakness creates a persistent threat vector that can operate continuously in the background without user awareness or intervention.
The technical exploitation of this vulnerability occurs through the service worker's ability to repeatedly trigger its own activate event, effectively creating an infinite loop that keeps the worker active indefinitely. This perpetual activation mechanism bypasses normal service worker lifecycle management and allows the malicious code to maintain persistent access to system resources. The vulnerability specifically affects Firefox's handling of service worker activation events, where the browser fails to properly terminate or limit the frequency of activation cycles. This flaw is classified under CWE-691 as an Insufficient Control Flow Management, where the control flow of the service worker execution is not properly constrained, allowing for unbounded execution.
The operational impact of this vulnerability extends beyond simple persistent execution to include comprehensive user activity monitoring capabilities. Once activated, the malicious service worker can continuously background monitor user browsing patterns, including tracking visited IP addresses, domain names, and potentially sensitive navigation data. This monitoring capability creates significant privacy concerns as users remain unaware of the persistent surveillance, with the service worker operating entirely within the browser's trusted execution environment. The threat actor can leverage this persistent presence to gather extensive behavioral data, potentially including sensitive information about user activities, network access patterns, and online behavior.
The attack surface for this vulnerability is particularly concerning as it requires minimal user interaction to establish and maintain persistent monitoring capabilities. Once a malicious service worker is installed through a compromised website or malicious extension, it can immediately begin executing the perpetual activation loop without requiring additional user consent or interaction. This makes the vulnerability particularly dangerous in environments where users may not be aware of the extent of monitoring occurring. The persistent nature of the threat also means that traditional security measures such as browser restarts or temporary session clearing may not effectively terminate the malicious activity.
Mitigation strategies for CVE-2018-5179 primarily focus on updating to Firefox version 60 or later, where the service worker activation mechanisms have been properly implemented to prevent infinite looping. Organizations should implement comprehensive browser security policies that include regular updates and monitoring for vulnerable browser versions. The vulnerability demonstrates the importance of proper control flow management in web application architectures and highlights the need for robust lifecycle management of background processes. Security teams should also consider implementing browser security extensions or enterprise browser management solutions that can detect and prevent unauthorized service worker installations. This vulnerability aligns with ATT&CK technique T1185 which covers web shell deployment and persistence mechanisms, as the service worker effectively creates a persistent backdoor within the browser environment. Additionally, the vulnerability represents a significant risk under the broader category of browser-based surveillance attacks that can operate without user knowledge or consent.